I'm doing some fiberglass work on my deck right now and in four to five months I'm going to have the gelcoat ground down and re-done. I've heard and had limited experience with bare fiberglass delaminating if its left uncovered and exposed to the sun but I don't want to paint the work I've done only to have to strip it off in a few months when I got to apply the gel coat. Any suggestions? I'm in Guatemala so the sun is rather intense.

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That makes sense. I've never gel-coated before so I wasn't thinking about it as an option. My next thought was to lay an extra layer of mat down, paint it and then grind it all off when the time came to gel-coat. That would be much more work. Thanks for the help guys.

Yep. Gelcoat protects the polyester from UV. Basically the pigments don't let the sunlight through. Edit. The very outer layer may break down because like you said its mixed with polyester resin. that's why older boats get" chalky"